An automobile seat of the type disclosed in (FR 2 824 799) includes a so-called active headrest by means of which the headrest is moved against the head of the seat occupant during a rear-end collision involving the automobile in order to prevent the head from being subject to strong acceleration and striking the headrest. With the help of a locking process device, the headrest may be locked in its extended position thus preventing the headrest from returning to its initial position due to a rearward moving impact of the head.
In FR 2 824 799, release of an extended headrest occurs by means of a pre-tensioning element that works with a blocking device that may be released upon limiting acceleration so that the pre-tensioning element brings the restraining device or the headrest to its extended position. The locking process device by means of which the headrest is arrested in the extended position is formed by an engaging element that may be engaged by means of a pre-tensioning spring with an engaging recess.
Another active headrest is known from DE 100 60 764 C1. In this design, the headrest or restraining device is brought from its initial position into the extended position not by means of a pre-tensioning element, but rather by means of pressure element positioned in the seat back area. This pressure element is actuated by the back of the seat occupant moving rearward during a rear-end collision. The locking process of the restraining device and the headrest in the extended position results from an articulated lever design.
Further, DE 102 28 675 C1 reveals a pressure-actuated active headrest system in which the headrest may be arrested in its extended position. This locking is by means of engaging elements facing each other, whereby one of the engaging elements is mounted elastically. When the head strikes the headrest because of a rear-end collision, the elastic element is deformed so that the engaging elements engage with each other. If the force exerted by the head is not sufficient, the elastic element provides a return force so that the engaging elements become disengaged. The design described in DE 102 28 675 C1 provides for automatic release of the lock.
The disadvantage in the prior art headrest systems a disclosed in FR 2 824 799 or DE 100 60 764 C1 is the fact that arrestment of the headrest in its extended position is not reversible. Expensive de-installation or repair of the seat is required in order to release the lock, i.e., in order to make the seat suitable for normal use.
The disadvantage of the design per DE 102 28 675 C1 is that the period of time during which the headrest is locked may be too short. Also, reliable locking may also depend on the angle at which the head impacts the headrest.
Based on this state of the art, it is the one object of the invention to provide a headrest system of the known type so that reliable locking of the headrest in its extended position is possible, and also so the system is easy to repair.